The formula for preparation of the polyvalent antivenom used in treatment of poisonous snakebite in the United States has not been changed in over 30 years, yet our knowledge of venom composition has changed drastically in this period of time. Use of this antivenom is the only consistent therapy for poisonous snakebite. There are two main problems with the polyvalent antivenom. It is not very effective in preventing local tissue damage induced by snake venom poisoning, and its administration frequently results in allergic reactions. A specific aim of this research is to characterize venoms from U.S. poisonous snakes by high resolution liquid chromatography and electrophoresis, to determine the biological activities of their major components and to select the best venoms to use as immunogens to prepare a polyvalent antivenom for use in the United States to neutralize all of the biological activities of a wide range of venoms. To address the problem of allergic reactions, the antivenom will be purified by affinity chromatography to yield an antivenom which contains only antibodies to biologically important venom components. The long-term objective is to develop an improved antivenom for the treatment of poisonous snakebite in the United States which prevents systemic and local effects of a wide variety of venoms and does not induce allergic reactions.